The present invention relates to a graphic data processing system and, more particularly, to a graphic data processing system which is appropriate for increasing the processing rate.
A system of the prior art is constructed as follows, as is disclosed in European Patent Application, publication number 0146961 (Jul. 3, 1985): Pixel addresses composed of address information for designating addresses of an image memory and pixel position designating information for designating pixel positions in one word, which are designated by the addresses, are sequentially calculated. The one-word graphic data designated by the address information of the pixel addresses calculated are read out from the image memory. Then, with information decoded from the pixel position designating information of the pixel addresses for designating a plurality of bit positions corresponding to the designated pixel positions, only a predetermined bit expressing one pixel of the graphic data read out is subjected to a graphic logical operation. The result of this logical operation is written again in the image memory so that it may be displayed.
In the prior art described above, the one-word graphic data in the image memory are considered such that the processing performance may be equivalent to that for a monochromatic image irrespective of the bit number composing one pixel. In case the one-word graphic data in the image memory have information of plural pixels, no consideration is taken into the point that those plural pixels are processed simultaneously in parallel. When the plural pixels in one word are to be continuously processed, the graphic data in the same address of the image memory have to be accessed and processed a plurality of times, thus raising a problem that the processing rate is decreased.